Filament mounting assembly



Nov. 15, 1949 Filed Sept.

I lh.

IllIlm V. L. RONCI FILAMENT MOUNTING ASSEMBLY 2 shee'ts-sheet'l 4a so NOV. 15, 1i949 V, 1 RQNCI 2,488,331

FILAMENT MOUNTING ASSEMBLY Filed Sept. i4, 1948 2 SheeS-Sheeb 2 ATTORNEY'.

Patented Nov. 1.5, 1949 .UINI TETD STA FILAMEN'I.v MOUNTING ASSEMBLY Victor il.. '-Ronci, "Allentowmia., assignor sto Bell 1'Telephone Laboratories, Incorporated, ANew York, iN. ,'Yw aorpnrationsof Nen/York Application September 14, 1948, Serial No. '49;273

Glaims. .1

This invention A.relates-to' high' power' electronic discharge *devices and "more particularlytoflila- Vmentmounting assembliestherefor.

In `electronic discharge devices'ofrtheexternal anode typehaving a 'grid and filament linearly and coaxially related'to theiinner surfacefof'the anode `the operating characteristics -clepend "on the spacial relation ofth'e electrodes. :SinceTt-he lfilament usually employed in such devices "is formed o'f Wire'fo'ldedintoa 'desired configurationtc meet certain'voltage and 'current requirements,"it is essential` for v'the attainment-of constant operating characteristicsthatthe filament 'be uniformly spaced `withirespect'to Ythe'other cooperating electrodes.

Considerable difficulty`has A'been Vexperienced "dueto distortion of'the iilament strands "occasioned 'by "high "thermal operating `conditions which result Iin`breakage Wh/enfthe filament Lis placed under Ystrain and"bowing Vor changing its space relation "to the other electrodes. "These conditions considerably 'reduce the stability or curtailthe usefullife of the device.

'An object o't'his invention is to increase the efciency'm 'operation of high power 'discharge devices Another object of the"inventionis"tofeliminate torsional strains onthe lament strandsinthe mounting assembly.

"Aiurthcr object o'f :the invention'isto reduce the bowing tendency` o'f the" filament during high temperature operation, therebyto stabilize the characteristics of the device.

Another object of 'the invention is to permit' the lament'to assume a natural position free 'from distortion either'in` the cold or plastic state after assembly in the device.

A further object o'f'the invention'l'is'to maintain axial' linearityof 'the 'filament Vassembly so that the operating characteristics are constant.

"These objects are attained, in accordance with 'this invention, 'by the provision of a rugged mounting structure which'imposes no torsional orV axial. stresses on v.the delicate filament strands sothat the V4larnent is allowed to assume a normal and unstrainediposition in relation to the other cooperating electrodes. "This is accomvvplished by attaching the ends of aioldedlilament 'to conductors in' the stem, coupling the sections of 'thelamentto a central standard and mounting A'the standard in Aa'frictionless guiding sleeve member associated with'the stem. "This construction "permits the" filament strands to'expand Aand Acon- "tract uniformly and during expansion compen- 'sates' for residual elongation; by the weight offithe standardWrlerebybowing-orI lateral'displacement 'and curvature are prevented whilethelamenthis fin 'f an Iincandescent sta-te. rwFurthermore, as Jthe 'larnentpools-when `-'the heating currentisdis- .-.5 vcontinued, the 'i'ilamentweturns 4Jto its "original `'lengthnormallyand without contractile'stresses being imposed `by thed supportingassernbly.

J-A-fi3atirre fof th-e' inventiornre'latesito:thenrounting uof 'the 'filamentYsupporti'n-g standard =in-"t-he lo assembly ofthe device. This -involves -a-'\tubu1ar vsoclretmember -vaxiallysecured'to -a centrar-post "the laste-n1 4and provided with internal Vspaced concentric jewel bearings in which the standard "is reciprocally androtatably movable within* the i5 *limitso' thepositons'oi" the-lament strands-as ^the` lament norinallyexpandsarrd contracts during Voperationcff*theelevice.

A-Another lean-rre'of*the` inventionrelatesrtolthe yieldahle Jcoupling of vthelamentrand standard "with AJthe stem -whereby f the total Mweight-lof 'the Vstandard -is -impressed -"on the filament strands I'during l"their plastic deformation Nstage, tto Ypreventrthe strands "assuming curvilinear or -catenary form withrespect to'fthe =adj acentaelectrode lsurfaces hwhich would -result in 'variation w'in espacial relationrotheelectrodes.

A further feature of' the invention "relates to vthe alignmentl ofthe-bearings in thefs'leevesupporttoinsureaXial--mountnrgofthefilarnentnsfeo -sembiyHregardless-of the'reciprocal'andbrotative Amovements -of the lstandard during transition phases ofthe *lamentlintlie device. This-"ar- -rangel/nent-involvesapairo'synthetic-jewel-bear ings `mounted concentricallyein'opposite Vends 'of .',grthe K4support-ing sleeve -with Han uinner `tubular vspacerengaging'both' 'bearings anda metallic eyelet on the outerendoi"'the-sleeveto"locl the"bear "ting" assembly in4 position. "The standard-im the 'device' is in -a dependingrposition withY respect,` to llthe Asupporting sleeve during opera-tion Avsort-hat the `standard 'can ride lreelywithinthegsleeve in an axialidirection-and-therebyrnaintai-n'sucient gravitational pressure on the plasticstrandsto kprevent bulging "or Jbowing "of the strands "to change-the spacial 'relation "offthe Vlilarnent with 'respecttothe `adjacent electrodes 'ofi/the device.

"These 'and Joth er "features an'd' `advantages 'of Fthe invention -will`-be -more -clearly understood vfrom 'the following d'detailed description when I 'considered in -con-nection withftheeaccompanying drawings in'which:

fFig. vl is an-elevational yvievwlin;sectiorwoifone lformof -an electron'discharge deviceembodyinga 'filament supper-ting; assemblyilill-ustrativeioftthis ilin-venton;

Fig. 2 shows part of the structure of Fig. 1 in an enlarged cross-section View with the lament guiding assembly shown in greater detail;

Fig. 3 is a perspective view of the filament assemoiy snown in Fig. 1 illustrating the mounting support of the filament and the associated guiding support in aligned relation.

Fig. a is a pian view along the section Ii-ll of Fig. 1 snowing tne detail assembly oi' the components in conjoint relation;

Fig. 5 is a plan View of the shield structure taken on the line 5-5 of Fig. 1; and

Fig. 6 is an enlarged detail View in section of the coupling joint betweenthe guide sleeve and post in the stem of the device.

This invention is particularly applicable to electron discharge devices of the high power type, such as disclosed and claimed in United States Patent 2,17 3,679 issued September 19, 1939 to J. E.

Clark and V. L. Ronci. The improvements perwtain specifically to the mounting assembly to the filament structure in order to overcome diniculties due to bowing or bulging of the multiple .sectionsof the filament during high temperature v operation. The alteration in position of the central filament with respect to the other cooperating surrounding electrodes of the device results in unstable operating characteristics, due to varia- ,anode section of the vessel. A pressed or molded glass stem I5 is fused to the inner end of the sleeve I3 and is provided with the central portion I6 projecting inwardly along the axis of the .enclosing vessel and a pair of outwardly extending terminal projections I1, only one of which is shown in Fig. 1. An exhaust tubulation I8 is also provided in the stem and terminates in a sealed tip I9 adjacent the outer end of the portion I2 at the center thereof. The terminal projections are sealed to copper cup terminals 20 which support internal rigid lead-in conductors 2I and ,external flexible metal braided conductors 22.

The latter are attached to a pair of contact pins 23 on the metallic base 24 cemented to the end of the glass section with a central recessed cap of the base protecting the sealing tip I9.

A flanged metallic ring 26, of Kovar alloy, is sealed coaxially to the inner end of the sleeve portion I4 and provided with apertures to receive rigid posts 2l which are fixed to the ring by lock nuts. These posts extend within the upper end of the anode portion I and are bent inwardly and secured to a metallic collar 28, for example by rivets. A corresponding set of parallel rods or heavy wire supports 29 are also secured to the collar 28 in spaced relation between the rods 21 and A continuous helical wire the helix is coaxial with the anode. A shielding cap 3l terminates the grid structure to strengthen the assembly and forms a baille adjacent the closed end of the anode. The grid is connected to an external circuit by a strap 32 joined to transverse lead 33 attached to a cup terminal 34 sealed to the side of the glass section II of the vessel.

A tungsten or thoriated tungsten wire 35, for example of .045 inch or .050 inch diameter, is preformed into a double hairpin configuration, to provide a multisection or multistrand electron source extending along the length of the grid and anode and mounted within these elements. Since the material of the filament is extremely brittle in a cold state and quite plastic in an incandescent state, it is necessary to control and protect the delicate filament after complete manufacture of the device so that long life and stable operation are attained.

When the filament is substantially rigidly mounted in the device, many difficulties are encountered during manufacture and use in operation due to contact or shorting on the grid which closely surrounds the filament assembly, or hot spots on the anode occasioned by a shift in operating characteristics which tend to cause boiling of the cooling fluid at a low dissipation rate, or bowing of one or more of the strands toward the grid during high temperature operation, or sticking or fusing of the filament to the supporting joints of the assembly which results in .a tendency to bend the central support when the lament cools after use. Furthermore, experience has shown that changes in composition of raw materials, in finished parts and different assembly techniques have increased shrinkage loss of assembled devices during exhaust and final testing at a high rate.

The preformed filament 35 is supported at the folds or bights in the same manner, as disclosed in the patent hereinbefore mentioned, by a double closed hook or loop assembly 36 at the lower end, a single intermediate hook 31 at the medial junction of the filament to the supporting structure and the free ends are coupled to the rigid lead-in conductors 2| by socket rods 38. The hook assembly 36 is affixed to the lower end of a central standard or main axial support rod 39, preferably of tungsten. The intermediate insulatingly supported hook 3l is attached to the coupling rods 38 and a heat shield or deflector 40 having slotted portions, as shown in Fig. 4, to clear the socket coupling rods 38 is attached to the standard, the shield being transversely in line with the upper edge of the collar. Since the standard is movable with respect to the illament the attachment of the hook 31 to the rods 38 provides a positive position of Ythe upper bight of the lament to the mounting so that relative movement between the filament and hook during the heating cycle is prevented.

Former failures originate primarily in the galling or fusing of the filament bights to the upper hook and lower loop supports of the filament as a result of temperature and pressure conditions at the friction points of the lament and support in the structure. This diiliculty may be explained by following the motion of the lament during the heating and cooling cycles of the device in operation. When the filament is first heated, the two lower bights must move downward in the loops and conversely, upward when the filament, cools. This motion is relatively rapid, coming to equilibrium in a few moments. A slower motion takes place at the upper hook as the filament leads and standard are heated by conduction and `convection. The latter action tends to impart a rocking or rotary motion'to the lament structure,

The upper hook 31 is designed and so positioned and supported that the lament rests with the bight seated in the bend of the hook in both hot and cold equilibrium positions. During the interim periods, the filament rides with respect to the hook.

The galling or sticking action occurs when the filament is fused or contact-welded to the hooks at some points due to a combination of forces caused by friction between two metallic parts, high temperature and low pressure environment which result in distortion and permanent bowing of the ilament when cold and consequent snorting with the grid helix which surrounds the nlament structure. If sticking occurs while the lament is hot and in an expanded condition, the standard or central support rod will sometimes be displaced laterally by the contraction forces during cooling. If in the contracted condition, the filament will bow or assume a curved or catenary form. In either case grid to filament contact or shcrting will be the ultimate result.

As shown in Fig. 2, the connection i the standard on the stem is such as to permit longitudinal and rotative movement of the standard comparable to the movement of the filament to compensate for the forces imposed on the iilarnent during operational cycles. In this arrangement, a central post lil, preferably of tungsten, is sealed in the projection Irion the stem and forms a rigid anchor axially fixed on the coaxial glass section of the vessel of the device. This post supports a guiding sleeve or elongated tubular socket t2 which is provided with a short extension t3 surrounding the post, a shoulder it and an axial bore of uniform diameter terminating in a cylindrical recess @5 of smaller diameter. The stem heat shield it is spot welded to the shoulder M, as shown in Fig; 5, and provided with clearance apertures to permit the passage of the grid rods 2l and the filament leads 2l therethrough, the shield protecting the seals within the stem from the high heating energy generated in the device within the anode section.

A synthetic sapphire jewel bearing or bushing ring el is seated within the sleeve adjacent the shoulder formed by the recess l5 and a similar aligned bearing i8 is mounted in the outer end of the sleeve. These bearings are maintained in spaced and concentric relation by a tubular metallic spacer insert 59, of nickel, and the bearing assembly is locked in the sleeve by an annular cap or eyelet 5i? which projects from the open end of the sleeve, the eyelet being held to the sleeve by spinning the lip over the anged portion in contact with the bearing 4d The extension t3 of the guiding socket is welded. to the post il! by forming a side slot 5| therein, as shown in Fig. 6, and inserting a piece of welding material 52 in the slot so that when brazed the welding metal flows into intimate contact with the post il to form an external joint 53, as shown in Fig. 2. In addition, a transverse drill hole Eli extends through the wall of the sleeve adjacent the recess L35 to permit evacuation of the cavity within the guiding socket of the assembly and to aid in the spacing and assembly oi the various elements. For example, the end of the standard 39 may be spaced from the end of the socket cavity #i5 by inserting a piece of drill rod into the hole 4l to gauge the position of tne standard in the socket. Since the jewel bearings are coaxially aligned in the guiding sleeve and the internal diameter of the bearings is slightly larger: than the diameter of the tungsten standard 39 which extendsV into the sleeve, the standar-d will have free movement in the sleeve both axially` in and rotatably due to the frictionless contact of the standard in the guiding socket. Therefore, the standard while maintaining axial support of the iilament assembly is. permitted to assume any position relative to the filament so that distortion and bowing are prevented. In the relations presented by the filament bights, hooks and standard, the lower bights will always rest in the upper ends of the loops ofthe hook assembly 3S due to the weight of the standard imposed on the iilament and the standard will follow the motion of the iilament as it expands and contracts, the sliding and rotative move ments taking place between the bearings and the standard. Thus, even if galling of the lament to the hooks occurs there is no tendency to bend or bow the iilament or impose stresses on the standard so that snorting and variation in spacing of the nlament with respect to the grid are eliminated and the operating characteristics of the device are held uniform and constant throughout a greatly increased operating life of the device.

While the invention has been disclosedy in a particular embodiment, it is of course understood, that various modincations may be made in the detailed assembly and association of parts without departing from the scope and spirit of the invention as defined in the appended claims.

What is claimed is:

1. An electron discharge device. comprising an enclosing vessel having a stem at one end, a hollow electrode extending coaxially with respect to said stem, an axial standard projecting within said electrode, a iilamentary electrode supported by said standard and stem, and means between said standard and stem and engaging said standard whereby gravity is the sole force exerted on said filament to tension the strands.

2. An electron discharge device comprising an enclosing vessel having a stem at one end, a hollow electrode extending coaxially with respect to said stem, a multistrand ilament within said electrode, a sleeve member fixed to said stem, and a central standard supporting said lament and slidably movable within said sleeve to apply gravity tension to said filament.

3. An electron discharge device comprising an enclosing vessel having a stem at one end, a hollow electrode extending coaxially with respect to said stem, a multistrand lament concentric with said electrode, an axial standard extending through said stem, said filament being @connected between said stem and one end of said standard, and a tubular member on said stem enclosing a portion of said standard, said standard being reciprocally and rotatably movable in said tubular member to apply gravity weight to said lament for tensioning the same.

4. An electron discharge device comprising an enclosing vessel having a stem at one end, a hollow electrode extending coaxially with respect to said stem, a multistrand lament concentric with said electrode, an axial standard extending from said stem, said lament being connected between said stem and the end of said standard remote therefrom, a metallic sleeve projecting from said stem, spaced ring bearings within said sleeve, said standard being embraced by said bearings to maintain axiality of said standard, and means associated with said sleeve for securing said bearings therein.

'5. An electron discharge device comprising a stem and a filament assembly including a rigid support projecting from said stem, a tubular socket attached to said support, a pair of spaced frictionless bearing members secured in said socket in linear relation, a loose standard in said socket and engaging said bearing members and a lamentary element carried -by said standard and attached to said stem.

6. An electron discharge device comprising an enclosing vessel having a stem at one end, a hollow electrode extending coaxially with respect to said stem, a multistrand larnent concentric with said electrode, an axial standard extending from said stem, said lament being connected between said stem and the end of said standard remote therefrom, a metallic sleeve projecting from said stem, synthetic sapphire annular bearings tted within said sleeve, a tubular spacer between said bearings, and an annular cap on the end of said sleeve securing said bearings and spacer therein, said standard extending into said sleeve and being positioned by said bearings.

7. An electron discharge device comprising a vessel having a metallic portion serving as an anode and having also a stem portion, a support rod sealed in said stem portion, a multistrand coaxially mounted Within said metallic portion, a central standard connected to said lament adjacent the end within said metallic portion, the free ends of said filament being joined to said stem, a rigid guiding sleeve member attached to said rod, and a disc shield on said sleeve member, said standard extending into said sleeve member for unbiased reciprocal axial movement with respect to said filament.

8. An electron discharge device comprising an enclosing vessel having a stem, and a filament assembly within said vessel including a rigid support projecting from said stern, a tubular socket attached to said support, a loose standard seated in said socket, and a lamentary element carried by said standard and attached to said stem.

9. An electron discharge device comprising a vessel having a metallic Yportion'servirlg as an anode and having also'a stem portion, a support rod sealedin said stemY portion, a multistrand filament coaxially mounted within said metallic portion, a central standardV connected to said filament adjacent the end within saidy metallic portion, the free ends of said lament being joined to said stem, and a rigid guiding sleeve member surrounding said rod having a notch for welding said rod to said sleeve and a flush brazed joint between the inner end of said sleeve and said rod for securely fastening said sleeve to said rod, said standard extending into said sleeve member for unbiased axial movement with respect to said filament.

10. An electron discharge device comprising a vessel having a metallic portion serving as an anode and having also a stem portion, a support rod sealed in said stem portion, a multistrand filament coaxially mounted within said metallic portion, a central standard connected to said lament adjacent the end within said metallic portion, the free ends of said lament being joined to said stem, a rigid metallic socket attached to said rod, a pair of aligned jewel bearing rings ywithin said socket, a metallic sleeve spacer in contact with said bearings at opposite ends, and an apertured cap member connected to the open end of said socket to hold said bearings.

and spacer in position therein, said standard loosely depending from said Socket to impose the weight of said standard on said lamentfor tensioning purposes.

VICTOR L. RONCI.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,113,671 Zottu et al. Apr. 12, 1944 2,350,270 Atlee May 30, 1944 2,385,435 Werner et al Sept. 25, 1945 

